Plasmas with 120hz refresh?

[swimmer_sf]

It seems to my lay-person's understanding that 120hz refresh is a feature found only on LCD's and that plasmas don't have the "artifact" problems that LCD's have in the first place with the 3:2 pulldown. Am I right? Anyone know what the difference is between LCD and plasma in this regard? Thanks!

[Nmlobo]

Not true at all. Any display that resorts to 3:2 pulldown can/will have 'artifact' problems.

[tower101]

Originally Posted by swimmer_sf

It seems to my lay-person's understanding that 120hz refresh is a feature found only on LCD's and that plasmas don't have the "artifact" problems that LCD's have in the first place with the 3:2 pulldown. Am I right? Anyone know what the difference is between LCD and plasma in this regard? Thanks!

Depends what "artifact" problem you are talking about. Most/all LCD's with 120 still do 3:2 pulldown.

Like Nmlobo said any TV that does 3:2 will have the same "problem" just like almost every TV ever made.

[swimmer_sf]

Tha'ts odd. I've been reading other threads and articles that say that 120hz means that 3:2 pulldown is no longer necessary for a 24fps movie because the tv simply displays each frame 5 times. I've also read quite a few articles saying that LCD tv's generally have more trouble displaying smooth fast-motion scenes than plasma tv's, and that's why LCD manufacturers are now introducing 120hz refresh rates. But I haven't heard that any plasma-tv manufacturers are introducing 120hz displays. Does anyone have direct information on plasma tv's and refresh rates of 120hz? Or do refresh rates simply not matter as much with plasma tv's? Thanks again folks.

[xrox]

Originally Posted by swimmer_sf

Tha'ts odd. I've been reading other threads and articles that say that 120hz means that 3:2 pulldown is no longer necessary for a 24fps movie because the tv simply displays each frame 5 times. I've also read quite a few articles saying that LCD tv's generally have more trouble displaying smooth fast-motion scenes than plasma tv's, and that's why LCD manufacturers are now introducing 120hz refresh rates. But I haven't heard that any plasma-tv manufacturers are introducing 120hz displays. Does anyone have direct information on plasma tv's and refresh rates of 120hz? Or do refresh rates simply not matter as much with plasma tv's? Thanks again folks.

I would suspect that Plasma displays will eventually go to 120Hz. There has been little pressure to do so because 120Hz main driving force is to improve motion blurring caused by LCDs "hold-type" nature, and plasma is already a stellar performer in this case. However, 120Hz offers the advantage of reducing judder and reducing flicker in plasma displays. Not to mention it will aslo improve upon it's motion performance.

But in order for plasma to use higher refresh rates it must greatly improve efficiency. This is because it uses PWM to produce grayscale. And since 120Hz reduces the frame time by 50% the display has to boost brightness by 50% to compensate.

Cheers

[tower101]

Originally Posted by swimmer_sf

Tha'ts odd. I've been reading other threads and articles that say that 120hz means that 3:2 pulldown is no longer necessary for a 24fps movie because the tv simply displays each frame 5 times. I've also read quite a few articles saying that LCD tv's generally have more trouble displaying smooth fast-motion scenes than plasma tv's, and that's why LCD manufacturers are now introducing 120hz refresh rates. But I haven't heard that any plasma-tv manufacturers are introducing 120hz displays. Does anyone have direct information on plasma tv's and refresh rates of 120hz? Or do refresh rates simply not matter as much with plasma tv's? Thanks again folks.

Some LCD's do 120hz but most still don't do 5:5 they are doing 3:2 then dubbeling that. 120 is more for blur then cadence.

No plasma does 120 (that I have heard of) as they don't need it, the new Poi changes it refresh rate to 72 when a 24 source is detected (4:4)

[Nielo TM]

Originally Posted by xrox

I would suspect that Plasma displays will eventually go to 120Hz. There has been little pressure to do so because 120Hz main driving force is to improve motion blurring caused by LCDs "hold-type" nature, and plasma is already a stellar performer in this case. However, 120Hz offers the advantage of reducing judder and reducing flicker in plasma displays. Not to mention it will aslo improve upon it's motion performance.

But in order for plasma to use higher refresh rates it must greatly improve efficiency. This is because it uses PWM to produce grayscale. And since 120Hz reduces the frame time by 50% the display has to boost brightness by 50% to compensate.

Cheers

That's right!

In modern plasmas, the phosphor will only emit light for about 4-6 milliseconds (hold-time) out of 16.6ms before it begins to fade, which causes slight flicker but at the same time, it helps to remove the previous image from the eye’s retina.


Back in the day, plasmas used to have hold-time of 16ms, which caused really nasty screen burns in such a short period of time, and motion blur was similar to 7th gen LCDs. But since the hold time now dropped to 4ms average, burn-in and motion blur aren’t that bad anymore.


I am sure in few years; one of the manufactures will drop the hold-time even further to 1-2ms and increase the refresh rate to 100/120Hz to reduce CRT like flicker. This would put the plasma right next to CRT in all departments.

[Nmlobo]

"Most" PDPs and LCDs are 60Hz displays. All 60hz displays have to perform 3:2 pulldown for 24fps material and are subject to associated artifacts, this includes plasma, lcd, crt, etc.

[tower101]

Originally Posted by XVN5

I am sure in few years; one of the manufactures will drop the hold-time even further to 1-2ms and increase the refresh rate to 100/120Hz to reduce CRT like flicker. This would put the plasma right next to CRT in all departments.

Damm I will have to upgrade again My wife is going to kill me

[Nielo TM]

Originally Posted by Nmlobo

"Most" PDPs and LCDs are 60Hz displays. All 60hz displays have to perform 3:2 pulldown for 24fps material and are subject to associated artifacts, this includes plasma, lcd, crt, etc.

There are some that can display true 100/120Hz. In any case, if a display was to advertise to have 100/120Hz (motion compensation), then it is refreshing at 100/120Hz.

As for 5:5 pull-down, it depends on the TVs video processor as some simply apply 3:2 and convert the 24Hz input to 60Hz, then apply motion compensation to convert 60Hz to 120Hz.

[swimmer_sf]

Wow, thanks for the interesting answers, which spawned another question. What is "flicker"? I currently have a CRT but I don't notice it flickering. Thanks!

[Nielo TM]

Originally Posted by tower101

Damm I will have to upgrade again My wife is going to kill me

You don’t have to worry about that anytime soon but, just in case, start working on you excuse now LOL

[Nielo TM]

Originally Posted by swimmer_sf

Wow, thanks for the interesting answers, which spawned another question. What is "flicker"? I currently have a CRT but I don't notice it flickering. Thanks!

If you display a white image on your CRT at 60Hz, you’ll immediately notice the flicker. It’s like someone turning on and turning off a light at very high speed.

[swimmer_sf]

Two other questions:

Do LCD's use PWM to create greyscale?

So the individual light-emitting elements in an LCD cannot be switched off as quickly as the light-emitting elements in a plasma?

Thanks.

[Nielo TM]

Originally Posted by swimmer_sf

Two other questions:

Do LCD's use PWM to create greyscale?

No! They use Active Matrix to drive the liquid crystals which produces grey scales by filtering the light from the backlight.

Originally Posted by swimmer_sf

So the individual light-emitting elements in an LCD cannot be switched off as quickly as the light-emitting elements in a plasma?

Thanks.

In LCD, it can’t be done cos the light is not emitted the pixels but rather by a backlight. So LCDs have two types of response time: Liquid Crystal Response Time (LCRT) and Hold-Time (HT). Currently, the LCRT is well within the acceptable level but hold-time is still quite high.

Plasma on the other hand is much simpler. PWM only emit light for 4-6ms out of 16.6ms. Remember, at 60Hz, each frame is displayed at 16.6ms intervals (1000/60). So for the first frame, the PWM creates pulse that powers the phosphor for the first 4-6ms. After that, the light from the phosphor begins to fade until the next pulse.

I can’t go into any deeper than that cos I am not that familiar with display driving mechanisms.

[swimmer_sf]

Thanks much. That was quite interesting.

[xrox]

Originally Posted by XVN5

In modern plasmas, the phosphor will only emit light for about 4-6 milliseconds (hold-time) out of 16.6ms before it begins to fade, which causes slight flicker but at the same time, it helps to remove the previous image from the eye’s retina.

When I quoted this information several times over the past year I generalized because it was easier to understand. However, since now people are quoting this info and we are talking about flicker as well it is time to be more specific. Plasmas do in fact emit light over the entire frame period of 16.7ms similar to LCDs. However, since they use Binary PWM the beginning 10ms of the frame time is dark to dim at best because the pulse widths are short. And the remaining 4-6ms near the end of the frame will be very bright as the pulse widths increase. This is what causes flicker in plasma displays. And also what causes a percieved short hold time.

There is a great picture of this in another thread somewhere........

[xrox]

Originally Posted by swimmer_sf

Wow, thanks for the interesting answers, which spawned another question. What is "flicker"? I currently have a CRT but I don't notice it flickering. Thanks!

Flicker occurs when the display emits light for only a portion of each frame period leaving the remaining portion black or dark. This results in a strobing or scanning perception to the viewer. In the case of CRT the display emits light for only 1-2ms per frame period of 16.7ms. If you cannot see flicker in this case then you have nothing to worry about in future displays.

Note: CRTs also raster scan the frame while digital displays use an all-at-once display method that contributes to flicker as well.

[xrox]

Originally Posted by swimmer_sf

Two other questions:

Do LCD's use PWM to create greyscale?

So the individual light-emitting elements in an LCD cannot be switched off as quickly as the light-emitting elements in a plasma?

Thanks.

LCDs modulate the voltage on each cell to create grayscale. The magnitude of the voltage determines what orientation the crystals are and thus how much light from the backlight can transmit to the viewer.

[xrox]

Originally Posted by XVN5

No! They use Active Matrix to drive the liquid crystals which produces grey scales by filtering the light from the backlight.


In LCD, it can’t be done cos the light is not emitted the pixels but rather by a backlight. So LCDs have two types of response time: Liquid Crystal Response Time (LCRT) and Hold-Time (HT). Currently, the LCRT is well within the acceptable level but hold-time is still quite high.

Plasma on the other hand is much simpler. PWM only emit light for 4-6ms out of 16.6ms. Remember, at 60Hz, each frame is displayed at 16.6ms intervals (1000/60).

I can’t go into any deeper than that cos I am not that familiar with display driving mechanisms.

Good expalanation except that I would say that Plasma is one of the most complicated display systems EVER! Much more complicated than LCD and OLED and even more than SED.

Cheers

[D-Nice]

Originally Posted by xrox

There is a great picture of this in another thread somewhere........

[swimmer_sf]

Really interesting information here. But I'm curious about this flicker phenomenon. It sounds like it's something you really have to try to see, otherwise people wouldn't buy plasma or CRT monitors. So why is it an issue at all?

[Nielo TM]

Originally Posted by xrox

When I quoted this information several times over the past year I generalized because it was easier to understand. However, since now people are quoting this info and we are talking about flicker as well it is time to be more specific. Plasmas do in fact emit light over the entire frame period of 16.7ms similar to LCDs. However, since they use Binary PWM the beginning 10ms of the frame time is dark to dim at best because the pulse widths are short. And the remaining 4-6ms near the end of the frame will be very bright as the pulse widths increase. This is what causes flicker in plasma displays. And also what causes a percieved short hold time.

There is a great picture of this in another thread somewhere........

oh, its the other way around.

Thanks for the heads up

[Nielo TM]

Originally Posted by swimmer_sf

Really interesting information here. But I'm curious about this flicker phenomenon. It sounds like it's something you really have to try to see, otherwise people wouldn't buy plasma or CRT monitors. So why is it an issue at all?

Flicker is actually a good thing (as long as it's minimal).

[swimmer_sf]

And flicker is good because it prevents images from blurring?